www2 most likely means that that you have been sent to their 2nd web server directly -- possibly they do not have load balancer properly configured .. or it is configured this way on purpose, so once redirected user stays there and not hitting balancer again.

Shopping.com does it all the time (at least did it in the past).

It also could mean that it is temporal redirect -- their main server is currently unable to handle the load (or not working completely) and you have been redirected to backup/secondary server for the time being. It is possible that if you visit this www2 URL next time (in few hours/days/weeks) you may be redirected back to their main web server (www).

It didn't must have to be the second webserver. I saw university-servers with subdomains named like chaos.
–
feeelaJul 5 '11 at 12:56

2

@feeela Yes, it could be just normal subdomain for no apparent reason. But if content is the same, then the chances are much higher that this is a second server .. or different code behind -- testing new code, DB structure or updated components/classes.
–
LazyOneJul 5 '11 at 12:59

WWW prefix
Many domain names used for the World Wide Web begin with www because of the long-standing practice of naming Internet hosts (servers) according to the services they provide. The hostname for a web server is often www, in the same way that it may be ftp for an FTP server, and news or nntp for a USENET news server. These host names appear as Domain Name System (DNS) subdomain names, as in www.example.com. The use of 'www' as a subdomain name is not required by any technical or policy standard; indeed, the first ever web server was called nxoc01.cern.ch, and many web sites exist without it. Many established websites still use 'www', or they invent other subdomain names such as 'www2', 'secure', etc. Many such web servers are set up such that both the domain root (e.g., example.com) and the www subdomain (e.g., www.example.com) refer to the same site; others require one form or the other, or they may map to different web sites.

Domain names preceded the world wide web, so back in the day, whatever.edu didn't necessarily mean a website. If there was a gopher server there, it was probably pointed to gopher.whatever.edu -- likewise with telnet.whatever.edu, ftp.whatever.edu, etc. It was common practice to prefix the domain name with whatever services was being offered there. So when the world wide web came along, it became common practice to prefix the web server with www.

Then, after time, since most people accessed only the website and not telnet or gopher services, administrators made it so that whatever.edu pointed to the webserver directly, and the www became optional.

So long story short, you can prefix your domain names with whatever you want. www2 is what wisc just wanted to point this service to, for whatever reason. They could have called it 2ndwebsite.biotech.wisc.edu if they wanted.

The www2 is a result of DNS or router load balancing. It is one of a set of web servers defined this way where www3 or www4 might also exist. Any subsequent request will always be with the original server even after a period of time as to maintain session state. There are other ways of doing this, however, this is one of the oldest and most reliable methods of load-balancing web traffic but far from technically the best option. More transparent dynamic load-balancing can break session state if one server is taken out of the farm, however, systems have existed for well over a decade that makes this extremely unlikely. It is likely quite possible that more than one method of load-balancing is being used as a secondary level of precaution. It is also possible that older methods remained and have been adapted over time and that the company simply chose not to dismantle a schema that has worked well.